The present invention relates to medical electrodes Medical electrodes are adhered to a patient's body to either collect electricity from the body at selected points or to introduce electricity into the body at selected points. Monitoring electrodes and diagnostic electrodes are examples of the former type. So-called "TENS ELECTRODES" are an example of the latter type. The present invention is useful for either type electrode, but is especially adapted for use as a tens electrode.
The typical prior art tens electrode 1 (FIG. 4) includes a layer of facestock 5 adhesively coated on one surface. The facestock is of a nonconductive material and facilitates adhesion of the tens electrode to the patient's body. Adhered to the central portion of the facestock is a highly conductive dispersive layer 2, typically a tin foil layer, which is somewhat smaller in dimensions than the facestock layer. A conductive stud 3 and a conductive eyelet 4 combination function as the electrical contact for the electrode Each includes an upstanding post projecting upwardly from an outwardly radiating base. The eyelet post projects through a small aperture in the dispersive layer and in the facestock layer and into the interior of the stud post. The two are snapped together such that a portion of the dispersive layer and the facestock layer are sandwiched between the respective stud and eyelet bases. The dispersive layer and eyelet base are then covered by a moderately conductive gel layer 6. The gel layer is slightly larger in dimensions than the highly dispersive layer to insure that the dispersive layer does not make direct contact with the patient's body. The function of the highly conductive dispersive layer is to insure that an electrical charge entering through the stud and eyelet connector is dispersed outwardly and evenly across the surface of the gel layer. The gel layer then conducts the dispersed electricity generally evenly into the patient's body.
The gel layer is somewhat smaller in dimensions than the facestock layer so that a portion of the adhesive surface of the facestock layer continues to remain exposed to facilitate adhesion of the entire electrode assembly to the body.
As manufactured, a layer of release liner 7 is provided to cover the entire surface of the facestock and the exposed gel layer. A small "thumb tab" 8 is typically adhered to a portion of the facestock adhesive surface between that surface and the release liner to facilitate peeling the release liner away from the facestock when it is time to use the electrode.
One problem with such a construction when used as a tens electrode is that hot spots tend to be created in the gel layer. There tend to be higher concentrations of electricity directly below the base of the conductive eyelet than in those portions of the gel layer located below the exposed surface of the dispersive layer. It is believed that this results from a tendency for electricity to flow more easily through the silver plated eyelet to the eyelet base than through the conductive dispersive layer.